And in This Corner ... David
The Equipment: Visonik D-50 loudspeaker system in plastic case.
Dimensions: 4 1/2 by 6 3/4 inches (front), 4 1/2 inches deep.
Price: $109.50 (also available as mobile unit, D-502M0, $122).
Warranty: "limited," five years parts and labor (one year parts and labor for D-502M0).
Manufacturer: Heco-Hennel and Co., West Germany. U.S. distributor: Visonik of America, Inc., 1177 65th St., Oakland, Calif. 94608.
Comment: With an obvious reference to the Biblical youngster who felled a giant, Visonik of America has announced the German-made David line of loudspeakers. The D-50, sharing honors for runt of the litter with the slightly more efficient D-30, constitutes a bare but hefty handful with a sound that belies its tiny size.
The cabinet is molded from a high-density, high-impact black plastic that appears very much like metal. A recessed slot on the back panel is provided so that the D-50 can be hung on a wall with a single screw. Connections are made via two binding screws on the rear with the polarity indicated by molded markings on the cabinet.
This is a two-way sealed system with a 3 3/4-inch long-throw woofer and a 3/4-inch soft-dome tweeter. No level controls are provided, but our listening tests (and the lab data) suggest that they are unnecessary. In the anechoic chamber at the CBS Technology Center, the average omnidirectional response was within ±3 dB from 100 Hz to 12.5 kHz. Over that range, that's one of the smoothest response curves we've seen. The front hemisphere and on-axis curves are very similar to the omnidirectional curve, with the response holding up to 16 kHz-the limit of the test-and indicate very good dispersion. Below 125 Hz, the response falls off smoothly at roughly 12 dB per octave.
The impedance curve is reasonably smooth and remains between about 3 3/4 ohms (the nominal impedance) and 15 ohms across the entire audio band. The average impedance of the system is more like 6 ohms (Visonik rates the speaker at 4 to 8 ohms), but we would caution against paralleling pairs of D-50s on a power amp not rated for a 2-ohm load.
In a speaker of this size, a smooth, extended response is not free, and (typically) the price is reduced efficiency. The average sound pressure level, measured omni-directionally from a 0-dBW noise input, is only 72 3/4 dB, or about 10 dB below average. David obviously is as power-hungry as its Biblical namesake.
Fortunately for its dynamic range, the system can digest the power it gobbles-especially in the midrange and highs. On a continuous basis, the D-50 will accept almost 20 dBW (100 watts) and deliver a sound pressure level a bit over 95 dB at 300 Hz before showing signs of breakup.
On pulses, the speaker accepts the full output of the lab amplifier -29 3/4 dBW (950 watts) peak--for a peak SPL of 105 dB.
While David does very well at reasonable sound pressure levels, its muscle is limited. This shows up in the distortion measurements. At 75 and 85 dB SPL (300 Hz), the third harmonic content is under 0.1%, much less than that of most speakers. Second harmonic is higher (0.22% at 75 dB SPL and 0.6% at 85 dB SPL)--about average. But at 95 dB, the D-50 does exhibit somewhat higher distortion than average and is subject to buzzing just beyond that. At a 0 dBW level, the combined second and third harmonic distortion remains below 1% at frequencies above 150 Hz. At 17 dBW (50 watts), the distortion stays below 6% at frequencies above 150 Hz. Below that (predictably, from the size of the woofer), the distortion increases sharply.
But small woofers have advantages to offset their limitations. The low mass improves transient response, and the small size approximates a point source radiator to a higher frequency. The 0-50, for example, has an exceptionally ac curate pulse response-in fact, one of the best we've seen. In the listening room, it shows excellent dispersion and transient response--again, equaling some of the best systems we've heard.
For our listening, we set the speakers flush against the front wall at about ear level. We found the amount of sound coming from those tiny boxes truly amazing. True, the lowest couple of octaves are missing and the distortion in the lower registers is more apparent than in many larger systems. But there isn't that much music in the very lowest octave, and the distortion apparently consists mostly of second and third harmonics, which are not particularly disturbing. Given a familiar harmonic array, the mind tends to fill in the fundamental even when it's not there. So these speakers subjectively have a lot more bass than test measurements would indicate, even though the lack of really low fundamentals is noticeable on timpani, organ pedals, and the like.
The midrange and treble are excellent, and the overall balance is very smooth. Both male and female singing voices are very well reproduced, and reproduction of brushed cymbals and brass instruments is exceptional.
The dispersion is excellent, and the stereo imaging has reasonable depth and fine lateral stability.
The David D-50 is an impressive loudspeaker, particularly in view of its compactness and price. It reproduces the major portion of the music spectrum and does so extraordinarily well. That its roar cannot equal Goliath's and its bass depends partly on psychoacoustic sleight of hand barely detracts from the convincing musicality of its illusion. And in the size of room that welcomes the minuscule dimensions of this speaker, such limitations of loudness and range are easily less than paramount. Given a powerful sling--an amplifier capable of 17 dBW or more will suffice--David can worry many a giant.
--------- FREQUENCY IN HZ
(High Fidelity, Oct. 1977)
Also see:
Technics SB-6000A floor-standing speaker system (Equip Profile, Oct. 1977)
KLH Model 35 speaker (Equip. Profile, Oct. 1977)
EPI Model 200 loudspeaker system (Equip. Profile, Oct. 1977)